Minimal Radiative Neutrino Masses

We conduct a systematic search for neutrino mass models which only radiatively produce the dimension-5 Weinberg operator. We thereby do not allow for additional symmetries beyond the Standard Model gauge symmetry and we restrict ourselves to minimal models. We also include stable fractionally charged and coloured particles in our search. Additionally, we proof that there is a unique model with three new fermionic representations where no new scalars are required to generate neutrino masses at loop level. This model further has a potential dark matter candidate and introduces a general mechanism for loop-suppression of the neutrino mass via a fermionic ladderComment: final version as published in JHE

Topological Transitions for Lattice Bosons in a Magnetic Field

We study the Hall response of the Bose-Hubbard model subjected to a magnetic field. We show that the Hall conductivity is proportional to the particle density plus an integer. The phase diagram is intersected by topological transitions between different integer values. These transitions originate from points in the phase diagram with effective charge conjugation symmetry, and are attributed to degeneracies in the many body spectrum which serve as sources for the Berry curvature. We find that extensive regions in the phase diagram exhibit a negative Hall conductivity, implying that flux flow is reversed in these regions - vortices there flow upstream. We discuss experimental implications of our findings.Comment: 11 pages, 7 figure

Design and Instantiation of IS2SAVE: An Information System to Predict the Influx of Spontaneous Volunteers at Operating Sites

Disaster managers are in charge of encountering natural disasters, yet, more often supported by citizens, so-called spontaneous volunteers. Their help has repeatedly been reported to be valuable for reducing disaster scales, regarding an increase in natural disasters occurrences with devastating effects. However, their characteristic to emerge in large groups has led to an unpredictable influx at operating sites from the perspective of disaster management. Finally, this led to problems such as congestions and blocked emergency routes, overcrowded operating sites and hampering officials in doing their work. To address this unpredictability, we apply a design science research approach to design and develop an information system to predict the influx of spontaneous volunteers at operating sites. We examine three design requirements and ten design principles, that we instantiate in a prototype. We finally validate our design theory empirically with experts, who positively highlight its perceived usefulness, conciseness, extendibility, explanatory power

A unique method for stochastic models in computational and cognitive neuroscience

We review applications of the Fokker–Planck equation for the description of systems with event trains in computational and cognitive neuroscience. The most prominent example is the spike trains generated by integrate-and-fire neurons when driven by correlated (colored) fluctuations, by adaptation currents and/or by other neurons in a recurrent network. We discuss how for a general Gaussian colored noise and an adaptation current can be incorporated into a multidimensional Fokker–Planck equation by Markovian embedding for systems with a fire-and-reset condition and how in particular the spike-train power spectrum can be determined by this equation. We then review how this framework can be used to determine the self-consistent correlation statistics in a recurrent network in which the colored fluctuations arise from the spike trains of statistically similar neurons. We then turn to the popular drift-diffusion models for binary decisions in cognitive neuroscience and demonstrate that very similar Fokker–Planck equations (with two instead of only one threshold) can be used to study the statistics of sequences of decisions. Specifically, we present a novel two-dimensional model that includes an evidence variable and an expectancy variable that can reproduce salient features of key experiments in sequential decision making.Humboldt-Universität zu Berlin (1034)Peer Reviewe

The Behavior of Spontaneous Volunteers: A Discrete Choice Experiment on the Decision to Help

Modern communication technology has enabled new ways to exchange information and is one of the main drivers for citizens’ participation in disaster response. During the last decades, so-called spontaneous volunteers have become an important resource in coping with disasters. However, their unpredictable behavior has also led to several problems. Disaster managers urgently need insights into volunteers’ behavior to effectively use the offered potential. To gain and provide these insights into explaining what drives the decision to help, we performed a discrete choice experiment based on previously identified behavior-affecting attributes. Our results indicate that attributes like the scale of the disaster and the media coverage are among the most important factors in the decision to help. The model correctly predicts volunteers’ scenario-specific decisions with an accuracy of 65\%. Hence, the experiment offers valuable insights into volunteers’ behaviors for disaster research and is a sound foundation for decision support for disaster management

Alignment-free sequence comparison with spaced k-mers

Alignment-free methods are increasingly used for genome analysis and phylogeny reconstruction since they circumvent various difficulties of traditional approaches that rely on multiple sequence alignments. In particular, they are much faster than alignment-based methods. Most alignment-free approaches work by analyzing the k-mer composition of sequences. In this paper, we propose to use \u27spaced k-mers\u27, i.e. patterns of deterministic and \u27don\u27t care\u27 positions instead of contiguous k-mers. Using simulated and real-world sequence data, we demonstrate that this approach produces better phylogenetic trees than alignment-free methods that rely on contiguous k-mers. In addition, distances calculated with spaced k-mers appear to be statistically more stable than distances based on contiguous k-mers

Time- and Frequency-Domain Dynamic Spectrum Access: Learning Cyclic Medium Access Patterns in Partially Observable Environments

Upcoming communication systems increasingly often tackle the spectrum scarcity problem through the coexistence with legacy systems in the same frequency band. Cognitive Radio presents popular methods for Dynamic Spectrum Access (DSA) that enable coexistence. Historically, DSA meant a separation solely in the frequency domain, while in recent years it has been extended through the dimension of time, by employing Machine Learning to learn semi-deterministic and cyclic medium access patterns of the legacy system that are observed through channel sensing. When this pattern is learnable, then a new system can utilize a neural network and predict future medium accesses, thus steering its own medium access. We investigate this novel and more fine-grained version of DSA, propose a predictor and show its capability of reliably predicting future medium accesses of a legacy system in an aeronautical coexistence scenario. We extend the predictor to the case of partial observability, where only a narrowband receiver is available, s.t. observations are limited to a single sensed channel per time slot. In particular, we propose a custom loss function that is tailored to partially observable environments. In the spirit of Open Science, all implementation files are released under an open license

Afterpulse Measurements of R7081 Photomultipliers for the Double Chooz Experiment

We present the results of afterpulse measurements performed as qualification test for 473 inner detector photomultipliers of the Double Chooz experiment. The measurements include the determination of a total afterpulse occurrence probability as well as an average time distribution of these pulses. Additionally, more detailed measurements with different light sources and simultaneous charge and timing measurements were performed with a few photomultipliers to allow a more detailed understanding of the effect. The results of all measurements are presented and discussed